Patent GB-645345-A (GB)
Title: Preparation of mineral-oil solutions of calcium or zinc salts of dithiophosphoric acid esters
IPC: C07F9/165
Filed: 1947-01-07
Abstract: Hydrocarbon oil solutions of calcium or zinc salts of oil-soluble esters of dithiophosphoric acid, suitable as additives for lubricating oils (see Group III), are prepared by adding the ester to a dispersion of calcium or zinc oxide, or hydroxide in mineral oil, said dispersion containing 0.1-5.0 per cent (e.g. 0.1-2.0 per cent) by weight of water.  The acid and basic materials are reacted together at 0-90 DEG  C. and the oil-insoluble reaction products also formed and any excess of oxide or hydroxide are removed from the solution by filtration. The formation of oil-insoluble reaction products is due to the ester not being a uniform product and to such reactions.  Suitable dithiophosphoric acid esters include dialkyl esters which may be produced from primary alcohols such as 2-methyl pentanol-1; 2,4-dimethyl pentanol-1; 4-methyl hexanol-1, and 4-methyl heptanol-1, or from secondary alcohols such as di-isopropyl carbinol. Dialkaryl esters produced from mono-, di- or tri-alkyl phenols, such as dodecyl phenol, di-octyl phenol, or tri-isobutyl phenol, may also be used.  In an example di-octyl phenol is heated with phosphorus pentasulphide and the reaction product neutralized by adding it to a suspension of lime in a low viscosity hydrocarbon lubricating oil containing about one per cent by weight of water.  The mixture is filtered.  Examples are also given of the preparation by similar methods of the calcium salt of the dithiophosphoric acid ester prepared from tri-isobutyl phenol and of the zinc salt of the ester prepared from a mixture consisting chiefly of primary and secondary alcohols of boiling range 160-200 DEG  C. (obtained by catalytic hydrogenation of carbon monoxide).  In the case of the zinc salt the product is partially dehydrated by treatment with anhydrous calcium sulphate to obtain a product which remains clear on cooling.  The Specification as open to inspection under Sect. 91 comprises also the preparation of heavy metal salts in general of esters of dithiophosphoric acid as described above.  This subject-matter does not appear in the Specification as accepted.ALSO:Mineral oil solutions of calcium or zinc salts of oil-soluble esters of dithiophosphoric acid, suitable for use as antioxidant additive concentrates for I.C. engine lubricating oils, are prepared (see also Group IV (b)) by adding an oil-soluble ester of dithiophosphoric acid to a dispersion of calcium or zinc oxide or hydroxide in mineral oil, said dispersion containing 0.1 to 5.0 per cent, e.g. 0.1 to 2 per cent, by weight of water.  The acid and basic constituents of the mixture are reacted together at a temperature between 0 DEG  and 90 DEG  C., and the oil-insoluble reaction products and any excess of oxide or hydroxide are removed from the solution by filtrating.  The formation of oil-insoluble reaction products is due to the ester not being a uniform product and to side reactions.  The solutions when added to lubricating oils used in internal combustion engines operating under severe conditions are said to reduce engine deposits and bearing corrosion. Suitable dithiophosphoric acid esters include dialkyl and dialkaryl esters.  The former may be produced from primary alcohols such as 2-methyl pentanol-1; 2,4-dimethyl pentanol-1; 4-methyl hexanol-1, and 4-methyl heptanol-1, or from secondary alcohols such as di-isopropyl carbinol.  The latter may be produced from mono-, di- or tri-alkyl phenols, such as tri-isobutyl phenol, di-octyl phenol, or dodecyl phenol.  The optimum results are said to be obtained when the proportion by weight of acid ester employed is substantially equal to, but not greater than, the proportion of oil dispersion.  In an example a solution prepared in the above proportions of the calcium salt of the dithiophosphoric acid ester (prepared from di-octyl phenol) in an S.A.E. 10 grade mineral lubricating oil is added in an amount of about 2 per cent by volume to a motor oil. The Specification as open to inspection under Sect. 91 comprises also the preparation of heavy metal salts in general of esters of dithiophosphoric acid as described above.  This subject-matter does not appear in the Specification as accepted.